another form of assistance concurrent with this capacity (1), such as causing the agent to will the act, for the act cannot be completed (2) without both capacity and will.

The capacity concurrent with the act includes firm will, unlike the capacity stipulated as a condition of obligation, for will is not a condition of the latter. Allah Most High (3) commands a person who does not will an act to perform it, but He does not command it of someone who, were he (4) to will it, would be incapable of it (5).

This distinction is the decisive word on this matter. The same applies when people command one another: a person (6) commands his servant to do something the servant does not will, but he does not command him to do something beyond the servant’s capacity. When firm will and complete power (7) come together, the act necessarily occurs. What thus necessitates the act must coincide with it; merely preceding it is insufficient if it does not remain concurrent with it. For it is the complete cause of the act, and a complete cause coincides with its effect rather than preceding it.

Moreover, capacity is a condition for the existence of the act [and for the agent’s being capable]; and where there is a condition for the existence of a thing [by which the capable agent is capable], [the thing] does not exist in that condition’s absence, but only in its presence (8). [Otherwise, the agent (9) would be acting when he was not capable, or someone other than (10) the capable person would not be capable] (11).